This invention relates to a heat transfer device and in particular to a heat transfer device for use in a gas barbecue.
All present gas fired barbecues use a porous lava or a similar material above a gas burner for cooking food placed on a grate above the lava bed. The lava and the air within the barbecue is heated by the gas burner and in turn heats the food. The lava also acts as a medium on which juices and fats are evaporated for heating the food and supplying the barbecue flavour.
The main problem encountered with the lava bed barbecue described above is flaming. The porous lava becomes saturated with fat and juices and ultimately ignites. Actually, the lava acts as a wick and the flame from the gas burner turns the lava into a torch. The obvious result is that the food must be removed or it will burn.
Various approaches have been taken to solving the problem of flaming in lava bed barbecues, including increasing the distance between the lava and the cooking surface on the assumption that if the food is kept sufficiently far from the lava, the speed or degree of burning due to flaming can be controlled. Another proposed solution is the use of cooking grates with grooves or channels carrying away some of the juices and fats so that they do not saturate the lava to the same extent as with ordinary food holding grates. Yet another method of solving the problem is the use of two burners, one on each side of the barbecue. The theory behind the twin burner approach is that by cooking on one side of the barbecue with only the burner on the other side of the barbecue operating, flaming can be avoided. While such a method is effective initially, ultimately the lava becomes saturated with fats and juices, which burn off when the barbecue is used again, i.e., when the burner on such side is ignited.
The major problem with lava is caused by the porous insulating qualities of the rock. Only very lightweight, porous lava can be used or other non-porous rocks may explode when heated to high temperatures. Because the lava is porous, it has excellent insulating qualities and does not readily transfer heat from the burner to the food. Moreover, because the lava is formed of individual pieces, there is poor heat conduction throughout the lava bed thus, most of the heat is transferred by high temperature convected air. These air currents are the main cause of uneven heating at the cooking area of the barbecue.
The object of the present invention is to solve at least partially the problems encountered with existing gas barbecues by providing a relatively simple substitute for the lava bed.